Children with medulloblastoma/PNET are currently treated with surgery, radiation, and chemotherapy. Survivors often suffer severe long-term toxicity from these treatments. Our laboratory has shown in ex vivo specimens from human medulloblastoma and mouse medulloblastoma models that targeted therapies including 13-cis retinoic acid (RA), cyclopamine, notch pathway inhibitors, histone deacetylase inhibitors and combinations of these agents induce medulloblastoma cell death as well as more toxic chemotherapy agents that are currently used for these patients. Based on our findings related to 13-cis RA, the Children's Oncology Group has developed a national Phase III clinical trial to assess efficacy of this agent. The broad long term goals of the biology correlative studies to this clinical trial are to 1) identify biomarkers with prognostic and predictive value for future clinical trials and 2) prioritize candidate targeted therapies for future clinical trials. The specific aims of this proposal are to utilize ex vivo surgical specimens to 1) identify biomarkers predicting therapy failure in high-risk medulloblastomas/SPNETs and 2) prioritize targeted therapies for future clinical trials. The significance of this work is that it is a direct means toward replacing current pediatric brain tumor treatment modalities with more effective and less toxic alternatives.